1. Field of the Invention
The present invention relates to an inductor. More particularly, the present invention relates to a symmetrical differential inductor.
2. Description of Related Art
Inductor is an important passive component, which is usually applied in radio frequency (RF) circuits, voltage controlled oscillators (VCOs), low noise amplifiers (LNAs), or power amplifiers (PAs), etc.
The magnitude of the inductance is usually relevant to the number of turns of the winded conducting wire, the geometric shape, and the material of the magnetic core. Quality factor (Q factor), i.e., Q value is a key index for determining the performance of the inductor. The general formula for the Q factor is shown as follows:Q=(stored electrical energy)/(consumed electrical energy).
It is known from the above general formula that, either increasing the stored electrical energy or decreasing the consumed electrical energy can enhance the Q value, so as to improve the performance of the inductor.
According to the signal transmission mode, the inductors may be divided into single-ended inductors and differential inductors. Generally, the differential inductor is usually a symmetrical spiral structure. In such a structure, the differential inductor usually has two ports, and voltages with opposite electrical properties and the same absolute value are applied on the two ports respectively. However, during the operation of the differential inductor, since the conducting wires of the symmetrical spiral structure are adjacent to each other, but have opposite electrical properties, a relatively large parasitic capacitance is generated between the neighboring conducting wires. In this way, the generated parasitic capacitance increases the consumed electrical energy; as a result, the Q value of the differential inductor reduces.